Design,Preparation And Properties Of New AlON Structure Luminescent Materials For N-NV W-LED

Due to the merits of low cost,extended lifetime,high quality and efficiency,the phosphor-converted white light-emitting diode?PC-WLED?has attracted more and more attention,and is considered as an effective substitute for the traditional incandescent and fluorescent lamp.Among them,matrix materials play a fundamental role.Among all kinds of compounds,aluminum oxynitride?AlON?is a kind of commonly used multi-functional matrix material.Because of its good physical and chemical stability,it has become a favorable choice.However,this kind of phosphors usually need harsh synthesis conditions,such as the preparation temperature up to 2000°C,and the pressure up to 0.5-1Mpa.On the other hand,rare earth ions have large radius,which makes them difficult to replace Al³⁺with small radius.So they can only enter the lattice gap channel,leading to a relatively single and nonadjustable emission spectrum.These two shortcomings greatly limit their production and application.In order to solve the above problems,based on the Al₅O₃N₃ system,a new polymorph of AlON structure,single-phase[Mg_1.25Si_1.25Al_2.5]O₃N₃,has been designed and synthesized by cation substitution method at a lower temperature.The luminescent properties with different rare earth ions doping were also studied.The main experimental results are as follows:?1?By appling the partial cation substitution method and changing the sintering temperature and flux,Single phase[Mg_1.25Si_1.25Al_2.5]O₃N₃ was successfully prepared at 1550°C.The crystal structure of[Mg_1.25Si_1.25Al_2.5]O₃N₃ has been studied by XRD.It is a central symmetric cubic crystal system composed of three kinds of[Mg/Si/Al]-[O/N]polyhedron,which is similar to other AlON systems.It could be observed that it has flake shape by various morphology analysis,and the element composition and relative content have been proved.?2?Eu²⁺was selected for single doping into[Mg_1.25Si_1.25Al_2.5]O₃N₃.There are two large Mg²⁺sites which could be replaced by Eu²⁺,leading to typical double site luminescent characteristics.Under the excitation of near ultraviolet light,it could exhibit ultra wide spectrum covering the whole visible light range,with color tunability and excellent thermal stability.It has a certain application potential as a single matrix near white phosphor.?3?Based on the above new AlON polymorph,Ce³⁺and Tb³⁺were selected for co-doping,and the results showed that they could occupy the position of the lattice gap.Through the efficient energy transfer of Ce³⁺to Tb³⁺,the green light with high brightness and narrow band could be realized.Under the excitation of 365nm and its optimum excitation 335nm,the luminous intensity can reach 78%and 113%of commercial green phosphor,respectively.The white LED with good performance could be obtained by encapsulating the as-prepared sample with the commercial blue,red phosphor and UV chip.